Field of the Invention
The invention relates to a cylindrical workpiece cutting apparatus, which cuts a metal made cylindrical workpiece into a plurality of metal rings.
Related Art
As a cylindrical workpiece cutting apparatus, an apparatus in which a cylindrical workpiece obtained by bonding both end edges of a metal thin plate is cut by irradiating the workpiece which is rotating with laser beam into ring shapes to form a plurality of metal rings is known (for example, refer to Patent Documents 1 and 2).    [Patent Document 1] US 2010/0200551    [Patent Document 2] JP-A-57-177896
The workpiece is rotated by holding the workpiece from an inner surface of the workpiece by a workpiece holder having a cylindrical outer surface and rotating the workpiece holder around an axis of a cylinder. The workpiece holder is provided with a plurality of slits extending in an axial direction, so that a diameter thereof can be elastically changed. The workpiece is held by disposing the inner surface of the workpiece to face the outer surface of the workpiece holder and enlarging the diameter of the workpiece holder.
During cutting the workpiece as described above, the metal configuring the workpiece is melted by the laser beam, is scattered as sputters or re-solidified and then is attached to cut parts as dross. In order to solve the problem, a hood has been provided to prevent the scattering of the sputters or a cooling medium for suppressing generation of the melted metal has been supplied.
For example, according to the cylindrical workpiece cutting apparatus disclosed in Patent Document 1, a passage for cooling medium is formed in a sidewall of a holding member that holds and rotates the cylindrical workpiece and the cooling medium is enabled to flow in the passage and to thus cool the workpiece, thereby avoiding the melting of the workpiece except for the cut part and suppressing the generation of the dross or sputters.
In the above apparatus, sublimated metal gas and melted metal, which are generated by the irradiation of the laser beam to the workpiece, are also sucked by a suction nozzle together with compressed air discharged from a discharge nozzle or the above cooling medium, so that the cut part remains to be clean.
However, even when the cooling medium is supplied or the suction is made by the suction nozzle, there may be cases the attachment of the dross ca not be prevented. The inevitably occurring sputters may be introduced into the workpiece holder through the slits, thereby interfering with the smooth enlargement/reduction of the diameter of the workpiece holder.
The sputters may also be attached and deposited in annular recesses of the workpiece holder, so that the holder and the workpiece or metal ring may contact each other. Thereby, a movement of the workpiece or metal ring relative to the holder is impeded or the workpiece or metal ring is damaged.